A solution to this issue may perhaps re-use some of the code in issue: "Add the ability to sort taxonomy facets by their term weight" - https://drupal.org/node/1361284
this image explains the need furher

| Comment | File | Size | Author |
|---|---|---|---|
| #3 | facet-sorting.jpg | 130.18 KB | sirtet |
| 2013 09 11 taxonomy facet filter - want sort alphabetically.png | 40.67 KB | therobyouknow |
Comments
Comment #1
therobyouknow commentedEven better would be to make this code generic for any sort, via a PHP interface and have the actual sort algorithm in a separate php class in a separate plugins folder and use dependency injection. This would enable people to write further kinds of sorts, though at the moment I can only think of weight and alphabetical.
Comment #2
summit commentedHi,
I support the possibility to order facets alphabetical!
Is this may be in the short future possible?
greetings, Martijn
Comment #3
sirtetIsn't sorting by "Display value" (2nd row in sort table) just what you want?

Comment #4
summit commentedHi, Yes I think that sort by "Display value" is what I want. Thanks!
If off course capitals are sorted as normal letters :)
greetings and thanks for your reply!
Greetings, Martijn
Comment #5
szeidler commented